Combustion apparatus

ABSTRACT

Combustion apparatus having a luminous element disposed within, and projecting above, a combustion plate. The light emitted by the luminous element, which will depend upon the state of combustion, is detected by a light detector, which through appropriate electronic circuitry containing various electronic components, will operate to control the air supply to the combustion housing whereby a proper combustible mixture for stable combustion is constantly being maintained. In like manner, the fuel supply may be controlled, in lieu of controlling the air supply.

United States Patent Ito et al. Oct. 16, 1973 [54] COMBUSTION APPARATUS 3,304,989 2/1967 Alexander et al. 431 79 [75] Inventors: Toshio Ito; Tamotsu Nomaguichi;

Masahiro Sakai; Koji f" of Primary Examiner-Edward G. Favors fiyogo'kenl Amagasakl, Japan Att0mey-Norman F. Oblon et al. [73] Assignee: Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan [22 Filed: Aug. 31, 1972 [57] ABSTRACT [21] Appl. No.: 285,376 Combustion apparatus having a luminous element disposed within, and projecting above, a combustion plate. The light emitted by the luminous element, [30] Forelgn Appllcauon Pnomy Dam which will depend upon the state of combustion, is de- Feb. 3, I972 Japan 47/12392 tected by a light detector, which through appropriate electronic circuitry containing various electronic com- [52] US. Cl. 431/75, 431/79 ponems will Operate to control the air supply to the [51] hit. Cl. F23" 5/08 combustion housing whereby a proper combustible [58] Field of Search 431/75, 79, 89, 328 mixture for Stable combustion is constantly being maintained. In like manner, the fuel supply may be [56] References C'ted controlled, in lieu of controlling the air supply.

UNITED STATES PATENTS 3,193,199 7/1965 Fuhs 431/75 4 Claims, 2 Drawing Figures l PM PAIENTEUIIBT 16 1915 FIG.

FIG.2

lI I I COMBUSTION APPARATUS BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates generally to combustion apparatus and more particularly to an improved combustion apparatus for stabilizing the flame of combustion within the combustion chamber.

2. Description of the Prior Art:-

One type of combustion system which has been widely employed in combustion apparatus is the diffu sion combustion system, practical embodiments of .which may include gun type combustion apparatus, pot

type combustion apparatus, and red flame type combustion apparatus utilizing gas combustion. In these combustion systems, the concentration of fuel, from 100 to percent fuel, has been dependent upon the atmosphere of combustion, so that the stability of the combustion has been remarkably high, which has accounted for the adoption of such systems of combustion in various fields.

However, such systems have serious disadvantages, in that, for example, it is possible to attain'incomplete combustion as a result of improper mixing of fuel and air. If, for example, the fuel is introduced into the combustion atmosphere when the mixing of the fuel and air is incomplete, the fuel component will be thermally decomposed so that only a portion of the fuel component will be burnt while the remainder results in the formation of soot. Consequently, although soot causes an increase in heat transmission from the combustion gases, at the same time, it also causes pollution of the air by increasing the percentage of carbon monoxide and nitrogen oxide.

One system which has been proposed as a method of eliminating the disadvantages of the diffusion combustion system is that system which prepares a primary gas mixture of fuel and air, such system resulting in a significant decrease in the formation of soot. However, such a system has also been plagued with serious problems,

such as, for example, in attaining optimum concentration of fuel and air within the primary gas mixture and of maintaining the stability of the flame of combustion while altering the fuel-air concentration.

Such problems are particularly concerned with the velocity of combustion and the fuel supply velocity. When, for example the fuel supply velocity is greater than the velocity of combustion, the flame is blown downstream, such phenomenon being known as a blown extinguishment. Similarly, when the fuel supply velocity is less than the velocity of combustion, the flame is sucked back into the flame holes, thereby causing a backfire. Complete combustion is thus impossible to attain and combustion is therefore intermittent whenever blown extinguishment or backfire occurs. Accordingly, it is desirable and necessary to prevent this unstable condition from occurring. Obviously, then, in order to maintain the stable condition of combustion, it is necessary to maintain the fuel supply velocity at a level which is less than the velocity, relative to the velocity of combustion, at which blown extinguishment occurs, but which is greater than the relative velocity at which backfire occurs. In addition, although the fuel supply velocity may be within the range for obtaining proper and complete combustion, combustion noise may be caused for some values of fuel supply velocity. Accordingly, it is also necessary for the fuel supply velocity to be without the range of velocities at which combustion noise will be produced.

Furthermore, at the optimum operating conditions for the combustion apparatus, the excess amount of air will be minimized for easily heat-exchanging the combustion air and the combustion gas. Likewise, complete combustion without the formation of soot, and stabilization of the flame of combustion, will similarly be attained. Accordingly, the unstable conditions of the flame of combustion occur when the optimum operating conditions are changed by external and internal causes. It is also noted however, that it is necessary to utilize combustion apparatus which is capable of operation under those conditions wherein a broader range of excess air will be required and which should be automatically controlled depending upon the change in operating conditions.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved combustion apparatus.

Another object of the present invention is to provide an improved combustion apparatus which will attain stabilization of the flame of combustion without the attendant conventional disadvantages. Still another object of the present invention is to provide an improved combustion apparatus which will automatically attain proper mixing of fuel and air under unstable combustion conditions so as to ultimately attain stable combustion.

Yet another object of the present invention is to provide an improved combustion apparatus which will prevent the occurrence of backfire or blownextinguishment, and which will also eliminate a substantial portion of the attendant noise of combustion.

The foregoing objectives are achieved according to this invention through the provision of combustion apparatus which employs a luminous element disposed within, and projecting above, the combustion plate. The light emitted by the element, depending upon the state of combustion then present, is detected by a light detector, which, through appropriate electroniccircuitry containing various electronic components, will control the amount'of air supplied to the combustion housing. In this manner, if the state of combustion should approach either of the extreme unstable conditions, that is, back-fire, or blown-extinguishment, the air supply will be automatically adjusted so as to return the apparatus to stable combustion operation. In lieu of controlling the air supply, the apparatus may be utilized so as to control the fuel supply.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advan tages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in con nection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views and wherein:

FIG. 1 is a schematic scetional view of one embodiment of a combustion apparatus constructed according to this invention and showing its cooperative parts; and

FIG. 2 is a schematic view of the control means for controlling the air supply of the combustion apparatus illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and more particularly to FIG. 1, there is shown a combustion apparatus, generally indicated by the reference character 1 comprising a cylindrical combustion housing 2 having transversely disposed therein a combustion plate 3 which, having a plurality of flame holes, serves as a buyner. A luminous element 4, which may be, for example, a platinum wire, is fitted within, and projects above, combustion plate 3. The location of plate 3, relative to housing 2, divides housing 2 into a lower mixing chamber 5 for mixing fuel and air, and an upper combustion chamber 6. A light detector 7, which may be, for example, a CdS photoelectric element, is connected to the combustion housing 2 at a point such that it can detect light emitted from luminous element 4.

Referring now to FIG. 2, the control means for controlling the air supply of the combustion apparatus is shown in detail. A light detectingmeans 8, including light detector element 7, is electronically connected to a controller 9 which controls the air supply to be delivered to the combustion housing 2. Controller 9, which is generally indicated by the dotted outline portion, comprises an amplifier 10 for amplifying the signal from detecting means 8, a thyristor short angle control circuit 11 and a bidirectional thyristor 12 for controlling the electrical output of an AC power source 13. An air supplier 14, such as, for example, a blower, is electronically controlled by source 13 while an air duct 15 is provided for conducting the air supplied by blower 14 to the combustion housing 2. A fuel supplier 16 for supplying fuel to the combustion housing 2 is likewise provided, the fuel being conducted to housing 2 via fuel supply pipe 17.

In operation, when combustion which has been in a stable condition, is altered by any one of various cases so as to approach a back-fire condition, wherein the flame of combustion will be upon the surface of the burner 3,the platinum wire 4, fitted upon the surface of the burner 3, will be heated and become luminescent. The platinum wire 4 thereby provides light which is distinguished from that of the flame, and the change in the light emitted by the platinum wire is received by the CdS photoelectric element 7 which results in the inner resistance of the CdS photoelectric element 7 being decreased so as to increase the electric current being passed through element 7. This change in current flow is then amplified by amplifier 10, which parameter is then fed to the thyristor short angle control circuit 11 so as to decrease the short angle of the bidirectional thyristor 12. The rotary speed of the blower l4is consequently increased, and an excess of air is supplied so as to stabilize the combustion flame.

At the other extreme, when combustion approaches the state in which the flame of combustion could be blown extinguished, the flame is located above the surface of plate 3 whereby the wire 4 is not heated and consequently its temperature and light emission decreases. It is thus seen that the light emitted is directly proportional to the heat of combustion received by the element. The resistance of the CdS photoelectric element 7 is thereby increased causing the electric current passing through element 7 to be decreased. After passing through amplifier I0 and control circuit ll, the resuiting current causes the short angle of the bidirectional thyristor 12 to be increased so as to decrease the rotary speed of the blower 14. This in turn reduces the excess amount of air being supplied, which results in the lowering of the flame and its ultimate stabilization. This stable condition of combustion can thus be automatically maintained by repetition of these operations should the combustion become'unstable at any instant of time. In conjunction with such operations, it is noted that the maximum and minimum limits of the short angle may be determined by the resistance of the control circuit 11. In addition, the resulting change in the flame of combustion will not be instantaneous due to the large moment of inertia of the blower 14. However, the changes in the flame of combustion will be rapid enough in order that the extreme unstable conditions of combustion, that is, back-fire, or blownextinguishment, will not be attained.

In an experiment performed with the apparatus of the present invention it was possible to operate the apparatus in its stable condition within the range of i 50 percent of the change in the amount of fuel supplied to the combustion housing. Within the apparatus, although a CdS photoelectric element may be used as the light detector, it is also possible to use other photoelectric elements such as, for example, a photo-transistor, a sunelectric cell, or the like.

Similarly, although a variable speed blower may be employed as the control means for controlling the amount of air supplied to the combustion housing, it is also possible to control the amount of air'supplied, by other means, such as, for example, a control valve actuated within the air duct 15.

In addition,,the mode of operation is not limited to those'examples noted heretofore, and it is entirely possible to control the amount of fuel supplied to the combustion housing in lieu of controlling the air supply to the housing, such fuel supply being regulated by control means similar to those control elements disclosed heretofore. Accordingly, the present invention provides combustion apparatus for stabilizing the state of combustion by controlling either the fuel supply or the air supply being conducted to the combustion housing.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood therefore, that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of The United States is:

l. Combustion apparatus comprising: a fuel supplier for supplying fuel to said combustion apparatus; r

an air supplier for supplying air to said combustion apparatus;

a mixing chamber for mixing said fuel and air supplied to said apparatus;

a combustion plate for igniting said fuel and air mixture within a combustion chamber;

a luminous element disposed within said combustion plate, said luminous element emitting light in an amount which is directly proportional to the amount of heat of combustion received by said elemom;

a light detector for detecting said light emitted from said luminous element; and

a control means electronically connected to said light detector for controlling the amount of air supplied by said air supplier.

2. Combustion apparatus as set forth in claim 1,

wherein said combustion plate contains a plurality of 5 flame holes and separates said mixing chamber from said combustion chamber, and wherein said luminous element projects from said plate into said combustion chamber.

3. Combustion apparatus as set forth in claim 1, wherein said control means comprises:

an amplifier for amplifying a signal emitted by said light detector; a thyristor short angle control circuit for receiving said amplified signal; and a bidirectional thyristor for receiving a signal from 

1. Combustion apparatus comprising: a fuel supplier for supplying fuel to said combustion apparatus; an air supplier for supplying air to said combustion apparatus; a mixing chamber for mixing said fuel and air supplied to said apparatus; a combustion plate for igniting said fuel and air mixture within a combustion chamber; a luminous element disposed within said combustion plate, said luminous element emitting light in an amount which is directly proportional to the amount of heat of combustion received by said element; a light detector for detecting said light emitted from said luminous element; and a control means electronically connected to said light detector for controlling the amount of air supplied by said air supplier.
 2. Combustion apparatus as set forth in claim 1, wherein said combustion plate contains a plurality of flame holes and separates said mixing chamber from said combustion chamber, and wherein said luminous element projects from said plate into said combustion chamber.
 3. Combustion apparatus as set forth in claim 1, wherein said control means comprises: an amplifier for amplifying a signal emitted by said light detector; a thyristor short angle control circuit for receiving said amplified signal; and a bidirectional thyristor for receiving a signal from said thyristor short angle control circuit for controlling the electric current of an AC power source which in turn electronically controls said air supplier.
 4. Combustion apparatus as set forth in claim 2, wherein said control means comprises an amplifier for amplifying a signal emitted by said light detector; a thyristor short angle control circuit for receiving said amplified signal; and a bidirectional thyristor for receiving a signal from said thyristor short angle control circuit for controlling the electric current of an AC power source which in turn electronically controls said air supplier. 